A vehicle is a means of transportation which produces power from an engine and transmits the produced power to wheels to transport a passenger or freight on a road.
The vehicle may be mainly divided into a vehicle body forming the external appearance of the vehicle and a chassis to which various devices are connected. The chassis includes principal devices, such as a vehicle engine which is motive power for travelling, a power transmission device, a steering device, a suspension device, and a brake device.
Most vehicle engines are four-stroke internal combustion engines. A four-stroke internal combustion engine is an internal combustion engine in which four strokes, such as an intake stroke, a compression stroke, a power stroke, and an exhaust stroke, constitute one cycle. Such a four-stroke internal combustion engine is the most common example of a reciprocating engine. An internal combustion engine, which mainly uses a volatile fuel, may directly obtain kinetic energy from thermal energy generated by compressing and burning the fuel in a state in which the fuel is fully mixed with oxygen in the air so that the fuel can be completely combusted.
The internal combustion engine, which uses such a volatile fuel, causes environmental pollution due to exhaust gas and also contributes to depletion of petroleum resources. An electric vehicle (EV), which is driven by electric current as power, has come to the front as an alternative to the internal combustion engine which uses the volatile fuel. The electric vehicle is a nonpolluting vehicle having no exhaust gas and noise. However, the electric vehicle has not been put to practical use due to high production cost, low maximum velocity, a short range, and overheating of a battery.
High oil price and recently strengthened restrictions on exhaust gas have increased speed in development of electric vehicles, and the market scale thereof is rapidly growing.